
The SOP is then defined as the probability that the secrecy rate \(C_S\)  falls below a threshold rate \(R_{th}\)  and is expressed as [1]}
\(\mathcal {P}_{out}&= \mathbb {P}\left[C_{S} < R_{th}\right]\nonumber \\&= \int _{0}^{\infty } F_{{\Gamma }_{D}}(\rho (x+1)-1) f_{{\Gamma }_{E}}(x) dx,\) 
